Researchers looked at more than 1800 teens from public schools in Boston, and tracked the amount of soda they self-reported drinking over the past seven days, and self-reported rates of violence.

What they found was that those who drank five or more cans of full sugar soda were significantly more likely to exhibit violent behavior, even when accounting for other factors like age and gender, alcohol and cigarette use, and average amount of sleep on a school night.

Overall, frequent soft drink consumers saw a 9%-15% spike in aggressive behaviors. There are, however, some issues with how the study was run. Ignoring the problem of this being self-reported soda-drinking, there's also an issue with how the study defined violence: "If [subjects] had been violent towards their peers, a sibling, or a partner, and if they had carried a gun or knife over the past year."

I don't know about your circles growing up, but everyone I knew who carried a knife in high school did so for practical purposes, usually a leatherman or simple folding knife. I'd also like to know what violence against a sibling amounts to, as siblings are commonly brutal to one another even if they don't otherwise have violent tendencies.

The authors ultimately admit there might not be a strict correlation between soda and violence:

"There may be a direct cause-and-effect-relationship, perhaps due to the sugar or caffeine content of soft drinks, or there may be other factors, unaccounted for in our analyses, that cause both high soft drink consumption and aggression."